1. Field of the Invention
This invention relates to a vibration-damping article and, more particularly, this invention relates to an article effective in reducing injuries caused by exposure to mechanical vibrations.
2. Background of the Invention
Tools which generate mechanical vibrations are ubiquitous in many work places. These tools include those directly powered by electricity and those which are hydraulically powered, e.g., by compressed air. Tools of this nature include grinders, drills, jackhammers, riveting guns, impact wrenches, chain saws, powered hammers, chisels, sanders, breakers, compactors, sharpeners, and shapers. When being used, these tools generate and transmit mechanical vibrations to the user""s hands. These mechanical vibrations may be classified by frequency. Those mechanical vibrations with frequencies of less than about 31.5 Hz are considered to be in the low (L) range. Mechanical vibrations with frequencies between about 31.5 Hz and 200 Hz may be considered to be in a medium or middle (M) frequency range. Mechanical vibrations with frequencies between about 200 Hz and 1250 Hz may be considered to be within the high (H) range.
Prolonged exposure by persons using, vibration-generating tools is considered to be a causal agent of Hand/Arm Vibration Syndrome (HAVS), also known as xe2x80x9cwhite-finger disease.xe2x80x9d HAVS is caused by prolonged exposure to mechanical vibrations and may be further exacerbated by working conditions in which colder temperatures are present. HAVS may result from exposure times ranging from one month to 30 years, or more, depending upon the intensity of the vibration source, the transmissibility and absorption of vibrations by the user, and the susceptibility of the individual to this disorder. Peripheral, vascular and neural disorders of the fingers and hands are characteristic of HAVS. Symptoms include numbness, pain, blanching of the fingers, loss of finger dexterity, and discomfort and pain in the worker""s upper limbs. HAVS can damage blood vessels, thereby reducing the blood supply to the user""s extremities. HAVS can also damage nerves in the user""s hands and fingers, thereby causing a permanent loss of feeling. Moreover, the user""s bones and muscles may become damaged as well. Consequences of HAVS may include loss of flexibility, the ability to grip or grasp objects, and, in extreme cases, gangrene. Because HAVS cannot be cured, prevention should be a major emphasis in the work place. Preventative measures, such as tools and articles of apparel designed to reduce the amount of vibrational exposure, should be utilized.
A substantial amount of frequency vibration is transmitted from power tools to the hands and upper extremities of workers. Workers who must stand on platforms may also be exposed to these deleterious vibrations. Efforts to mitigate, or attenuate, this unacceptable vibrational energy transmission have included using gloves with various protective materials. Examples of some of these efforts to manufacture and design gloves to attenuate vibrational exposure include those described in U.S. Pat. Nos. 5,632,045, 5,673,437, 5,822,795, and 5,987,705, the entire disclosures of each hereby incorporated by reference. Mitigation and vibration reduction to other parts of the body, e.g., the foot, has been disclosed in U.S. Pat. No. 4,627,179, the disclosure also hereby incorporated by reference.
In order to be safely and effectively used, tools must be easily and firmly grasped by the worker. To be safely and firmly grasped by the worker, handles and other surfaces grasped or gripped during use should have a cross-sectional dimension (e.g., a diameter) within a specified range. If gloves are worn, the cross-sectional dimension should be smaller to accommodate the thicknesses of the gloves. Thus, gloves and other shielding devices failing to provide an effective gripping diameter of between about 1.0 and 2.0 inches (e.g., 1.5 inch) may cause excessive and premature hand fatigue, thereby reducing the ability of the worker to effectively and efficiently control the tool being used.
Previously, gloves which protect wearers from vibration-induced injury have often limited the dexterity, e.g., the ability to pick up and manipulate objects, of persons wearing the glove.
Therefore, there is a need for a damping article which will damp otherwise harmful mechanical vibrations sufficiently to prevent the onset of HAVS, yet will provide for a grip which will enable a worker to effectively control the tool being used to prevent or greatly delay the onset of gripping fatigue and will provide for an enhanced dexterity.
This invention substantially meets the aforementioned needs of the industry by providing a substantially flexible article for damping mechanical vibrations. The article may include first, second, and third layers. The first layer may include a polymer capable of damping at least a portion of the middle range of mechanical vibrational frequencies such as neoprene. The second layer may include a viscoelastic polymer capable of damping at least a portion of the high range of mechanical vibrational frequencies such as a foamed polyurethane. The third layer may include a second viscoelastic polymer capable of damping at least a portion of the middle range of mechanical vibrational frequencies such as a non-foamed polyurethane. The first, second, and third layers may be disposed in a substantially overlaying relation. The article may be characterized by a medium range vibratory transmissibility of less than about 1.0, and a high range vibratory transmissibility of less than about 0.6.
It is an object of the present invention to provide an article which will damp mechanical vibrations so that injury to persons exposed to these vibrations is greatly or significantly reduced.
It is another object of the present invention to provide a vibration damping article which is dimensioned and configured to be inserted into a glove.
It is yet another object of the present invention to provide a vibration damping article which can be permanently provided in a glove.
It is still another object of the present invention to provide a vibration damping article with an article thickness dimensioned to provide an effective gripping cross sectional dimension to prevent or greatly reduce gripping fatigue.
It is a further object of the present invention to provide a vibration damping article with a reduced article thickness to enhance the dexterity and flexibility of a user""s hands when the present article is present in protective gloves.
It is yet still another object of this invention to provide a vibration damping article which will eliminate or greatly reduce the exposure of a wearer""s feet to injury by mechanical vibrations.